There is known, as one of output devices of computers and workstations, an image forming apparatus employing an ink-jet system in which ink is ejected to form an image on a recording sheet. The image forming apparatus employing an ink-jet system comprises, for example, a print head having a plurality of ink ejection outlets each for ejecting ink, a carriage on which the print head is mounted, said carriage reciprocating in a predetermined direction, and a conveying device for intermittently conveying recording sheets in a direction (a recording sheet conveying direction) intersecting perpendicularly to the predetermined direction.
In the event that an image is recorded on a recording sheet, the recording sheet in the course of conveyance by the conveying device is temporarily stopped, and while the carriage is reciprocated in the predetermined direction, ink is ejected from the ink ejection outlets in accordance with a control of the print head to form (print) a band of image on a portion located at an image formation area of the recording sheet. Thereafter, the recording sheet is fed by a predetermined length to form an image on a new portion located at the image formation area, of the recording sheet. Such a performance is repeated.
The conveying device comprises, usually, a drive roller having a drive roller axle extending in a direction intersecting perpendicularly to the recording sheet conveying direction, and a plurality of driven rollers each detachably mounted on the drive roller for pressing the outer peripheral surface of the drive roller. The drive roller and the driven rollers support a recording sheet in cooperation with one another and convey the recording sheet to the image formation area in such a manner that the recording sheet is sticked on the outer peripheral surface of the drive roller.
In the course of conveyance of the recording sheet in this manner, it happens that a jam occurs for example, around the drive roller. In case of the occurrence of the jam, there is a need to remove the recording sheet by separating the driven rollers from the drive roller. It happens, however, that a movable distance of the driven rollers for separation from the drive roller is too short to access the place at which the jam has occurred. Further, even if it is accessible, it happens that the recording sheet is broken because of insufficient grasp for the recording sheet. Consequently, in some cases, it would take a long time to solve the jam.
After solving the jam, the drive roller is pressed by the driven rollers and the recording sheet is conveyed while supported by the drive roller and the driven rollers. In this case, it happens that the driven rollers are out of their regular positions. In such a case, it happens that rotating the drive roller in some turns causes the driven rollers to take to the drive roller so that the driven rollers are regulated in their positions. However, in this case, it happens that the recording sheet is not conveyed in a proper conveyance direction during a period of time until the driven rollers have been regulated in their positions. Thus, there is a possibility that the jam again occurs.
Further, when the jam occurs, it happens that the carriage stops upward the driven rollers. In such a situation, when the driven rollers are separated from the drive roller so as to remove the recording sheet, there is a possibility that the driven rollers collide with the carriage or the print head which is mounted on the carriage, and as a result they are damaged.